Conventionally, silicon carbide semiconductor devices in which silicon carbide (SiC) is used have been known, and an example of them is disclosed in International Patent Publication WO01/018872 (hereinafter “Patent Document 1”) for example. Patent Document 1 discloses a MOS-type field effect transistor (MOSFET) that is formed as a silicon carbide semiconductor device using an SiC substrate of the 4H polytype having a surface orientation of substantially {03-38}. According to Patent Document 1 disclosing the MOSFET, a gate oxide film is formed by dry oxidation and a high channel mobility (about 100 cm2/Vs) can be achieved.